With XE on the Welcome Page I can manage my projects in "My
Favorites" and then arrange the projects into grouping.

How do I do this in the 10.2.3 IDE

Basically the same way. The layout of the welcome page may have changed
a bit, but the basic functionality is there. You have to open an
existing project or project group (in fact you should not try to open
an existing DPROJ file if it comes from XE, there have been a number of
changes to the project file handling since XE. It is safer to delete or
at least move to somewhere else the dproj file and then let the IDE
recreate it by opening the DPR file instead).

After you have closed the project in the IDE again the welcome page
will list it under the "recent files" section, and each of the entries
has a "add to favourites" link you can use to move it to the favourites
section.